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01 Record

CVE-2026-48819

Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key

MediumPUBLISHEDCNA: GitHub_M
CNA base score4.8 CVSS v3.xCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
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02 Description

Hey API: `buildClientParams` template: prototype chain substitution via unknown `$<slot>___proto__` key

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.27% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 19.3% of scored records. A rank, not a probability.
NVD base score
4.8 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD analysis status
Deferred. NVD last modified this record on 2026-10-24.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-07-17 19:46Z3 MO AGO
Last updated
2026-07-20 16:24Z3 MO AGO
Reserved
2026-05-22
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
Medium (CVSS 4.8)
CNA CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Weaknesses
  • CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')Variant
Data version
5.2
Document digest
62c086c403bfdcde65fa7d95beb53e0a9b19701787e74d2475f72e2fef9ed23d

05 Affected products

VendorProductVersionsPlatforms
hey-apiopenapi-ts< 0.97.3—

06 References